In the printing film-making industry, two types of films are used, namely roll films comprising a long sheet of film rolled around a core and sheet films comprising a sheet of film cut into a given size. Roll films are more commonly used because of their advantages such as easy handling and low price.
However, such roll films tend to have habitual curling due to film rolling, which poses a problem of poor handling property in sheet use, demanding improvement.
To solve the problem of habitual curling after development, some methods have been proposed, including the method of Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O. P. I. Publication) No. 244446/1989, which uses a film of copolymerized polyester comprising an aromatic dicarboxylic acid having a metal sulfonate. However, against the habitual curling in unprocessed films, there is no effective measure.